The invention relates to hand operated electric tools and particularly to a brake control for said tools.
The prior art includes a number of patents which in general disclose armature brakes for electric motors although a number of them are disc type breaks. Among the more pertinent references are U.S. Pat. No. 3,579,066 to Bearfield et al and U.S. Pat. No. 3,339,681 to Holladay. The Bearfield patent discloses an electric motor having a solenoid mechanism connected to a brake shoe which upon deactivation of the solenoid automatically engages a brake drum or the rotor of the electric motor due to the action of a spring thereby stopping the rotation of the motor. The Holladay patent essentially shows a solenoid actuated brake mechanism for an electric motor.
Also of interest is U.S. Pat. No. 515,755 to Dunn which in general discloses an electric motor in which a brake shoe is spring biased into engagement with a brake drum and released by the action of a solenoid.
Other prior art patents in this general area include U.S. Pat. Nos. 3,096,453, 3,176,173 and 3,335,304. These patents are representative of the existing art in the general area of the present invention and are not intended to be an all inclusive listing of the prior art.
The present invention is an improvement over the prior art noted above in that the brake device may be readily incorporated in a wide variety of rotary tools and is particularly suited for pistol shaped electric tools with the solenoid being positioned within the handle or grip of said tool and the brake itself being positioned in the barrel of the tool. The cam operation of spring biased brake shoes against the brake drum provides a safe immediate halt to the operation of the tool when pressure is released on the trigger. In electric drills, for example, the power may be cut immediately when the drill breaks through the material thereby preventing the possibility of the drill getting away from the operator. This is also essential when operating tools such as electric saws where physical injury may result from the continuous rotation of the blade.